Thanks for answering, Daniel!
The matter is that I've organized my trip in this part of Japan in the following way, in order to be able to reach Takayama on time for the Festival:
from Kamakura:
09/04/2013: Magome/Tsumago
10/04:Matsumoto
11/04: Kanazawa
12/04: Shirakawago/Takayama
13/04: Takayama
14/04: Takayama
15/04: Kyoto
which means that I'll be passing through Shirakawago/Takayama, but after Kanazawa...
I'm considering 2 possibilities:
Taking your advice and to face the 5 hours train ride via the north of Japan (in this case, what'd be the best option: via Nagano/Naoetsu, or Itoigawa?)
Changing my plans and to choose Nagano rather than Kanazawa, in order to make it easier! Is it a good change?
Any sugestion on the itinerary would be very welcomed!
Cheers
Denise